CN104201674A - Comprehensive load model modeling method considering load low voltage release features - Google Patents

Abstract

The invention provides a comprehensive load model modeling method considering load low voltage release features. Feature parameters such as critical voltage when large-amount load removing is started, the time delay of the time when the voltage falls to the critical voltage and the time when the large-amount load removing is started, and the proportion of the loads with low-voltage protection in total loads are introduced into an existing comprehensive load model considering a power grid to describe disturbance middle load low voltage release features. By the model, the defect that a traditional dynamic load model cannot describe the load low voltage release features is overcome, and accuracy and credibility of power system simulation calculation are increased.

Description

A kind of modeling method of integrated load model of the low-voltage release characteristics of considering to load

Technical field

The present invention relates to a kind of modeling method, be specifically related to a kind of integrated load model modeling method of the low-voltage release characteristics of considering to load.

Background technology

Along with the raising of Power System Interconnection degree, the dynamic characteristic of electrical network under fault becomes and becomes increasingly complex, for the fail safe that improves electrical network prevents the generation of the accident of having a power failure on a large scale, in Electric Power Network Planning and in service often needs, electrical network is fullyed understand in the characteristic under particular state.Because the requirement of electrical network self has determined to do in actual electric network and has tested Study system stability on the one hand, in addition on the one hand emulation institute for the running status anticipation situation in future often, in the middle of reality, also do not occur, so also determined the stability to electrical network to study in real system.Emulation has just become operation of power networks, planning, the requisite instrument of design in this case.

While repeatedly having there is disturbance in actual electric network, there is load low-voltage release phenomenon.Taking Shanghai Power Network as example, on June 27th, 1998, Shanghai accumulate the 220 switch blade mechanism case water inlets of No. 1 main transformer of algae creek, caused line to line fault, and the direct power failure load that this time accident causes is 200MW, but low-voltage discharges load up to 500MW.Main cause is the transient state low-voltage that Shanghai Power Network high-voltage fence phase to phase fault causes, and causes large quantities of induction motor load generation low pressure trips.In addition, in the fault recorder data of large disturbance, having there is the inconsistent situation of disturbance front and back steady-state value in the recorder data that also collects some transformer stations, has also occurred low-voltage release phenomenon northeastward.The low-voltage of loading while there is disturbance for actual electric network release phenomenon, existing load model is difficult to describe, therefore further investigation load low-voltage release characteristics, build the load model of considering load low-voltage release characteristics, have great importance to improving power system digital simulation accuracy in computation.

Due to electric load show low-voltage discharge characteristic in, also show the feature of the synthetic load of traditional induction motor load and static load composition simultaneously, therefore discharge in the process of modeling in the low-voltage of research load, should load model structure as basis taking tradition, outstanding its low-voltage release characteristics.

Summary of the invention

In order to overcome above-mentioned the deficiencies in the prior art; the invention provides a kind of modeling method of integrated load model of the low-voltage release characteristics of considering to load; critical voltage when introducing load start a large amount of excision in the integrated load model of existing consideration distribution network, from lower voltage to critical voltage, start the characteristic parameters such as the time delays of a large amount of excisions, ratio with the load of low-voltage variation in total load to load, be used for describing the characteristic that disturbance shoulder load low-voltage discharges.This model has overcome conventional dynamic load model cannot describe the shortcoming of load low-voltage release characteristics, has improved accuracy and confidence level that electric system simulation calculates.

In order to realize foregoing invention object, the present invention takes following technical scheme:

The integrated load model modeling method that the invention provides a kind of low-voltage release characteristics of considering to load, described integrated load model comprises static load model and induction-motor load model; Said method comprising the steps of:

Step 1: set up static load model according to static load low-voltage release characteristics;

Step 2: set up induction-motor load model according to induction-motor load low-voltage release characteristics;

Step 3: active power and the reactive power of determining integrated load model output.

In described step 1, when before electrical network breaks down and after fault, low-voltage release not yet occurs static load, active power and the reactive power of static load are expressed as:

$\left\{\begin{array}{c}{P}_s=P_{s0}[P_Z{(V/V_0)}^2+P_I(V/V_0)+P_P]\\ Q_s=Q_{s0}[Q_Z{(V/V_0)}^2+Q_I(V/V_0)+Q_P]\end{array}\right.$

Wherein, P _sand Q _sbe respectively electrical network break down before and fault after static load not yet occur low-voltage discharge time static load active power and reactive power; P _s0and Q _s0the active power of static load and reactive power while being respectively stable state; P _zand Q _zbe respectively constant impedance part active power ratio and reactive power ratio in static load; P _iand Q _ibe respectively constant current part active power ratio and reactive power ratio in static load; P _pand Q _pbe respectively firm power part active power ratio and reactive power ratio in static load; V is load bus virtual voltage amplitude, V ₀the busbar voltage of loading during for stable state amplitude;

If have m kind to meet low pressure release conditions with the static load of low-voltage protection device after fault clearance, the active-power P of static load _s' and reactive power Q _s' be expressed as:

$\left\{\begin{array}{c}{P_s}^{\′}=P_{s0}(1-k_{s1}-k_{s2}-...-k_{\mathrm{sm}})[P_Z{(V/V_0)}^2+P_I(V/V_0)+P_P]\\ {Q_s}^{\′}=Q_{s0}(1-k_{s1}-k_{s2}-...-k_{\mathrm{sm}})[Q_Z{(V/V_0)}^2+Q_I(V/V_0)+Q_P]\end{array}\right.$

Wherein, k _s1, k _s2..., k _smbe respectively with the 1st, 2 ..., m kind low-voltage protection device the ratio of static load in total static load.

In described step 2, when before electrical network breaks down and after fault, low-voltage release not yet occurs induction-motor load, induction-motor load meets:

$\left\{\begin{array}{c}\frac{{{\mathrm{dE}}_d}^{\′}}{\mathrm{dt}}=-\frac{1}{T^{\′}}[{E_d}^{\′}+(X-X^{\′})I_q]-(\mathrm{\ω}-1){E_q}^{\′}\\ \frac{{{\mathrm{dE}}_q}^{\′}}{\mathrm{dt}}=-\frac{1}{T^{\′}}[{E_q}^{\′}-(X-X^{\′})I_d]+(\mathrm{\ω}-1){E_d}^{\′}\\ \frac{\mathrm{d\ω}}{\mathrm{dt}}=-\frac{1}{2H}[({\mathrm{A\ω}}^2+\mathrm{B\ω}+C)T_0-({E_d}^{\′}{I}_d+{E_q}^{\′}{I}_q)]\end{array}\right.$

Wherein, E _d' be motor d axle transient internal voltage, E _q' be motor q axle transient internal voltage; T ' is motor open circuit time constant, T ₀for the benchmark machine torque of motor; A, B and C are machine torque coefficient; X is the reactance of rotor open circuit, and X=X _s+ X _m, wherein X _sfor stator reactance, X _mfor excitatory reactance; Stator equivalent reactance when X ' is rotor stall, and X '=X _s+ X _mx _r/ (X _r+ X _m), X _rfor rotor reactance; ω is the angular speed of rotor; I _dfor stator current d axle component, I _qfor stator current q axle component, be expressed as:

$\left\{\begin{array}{c}{I}_d=\frac{1}{R_s^2+X^{\′2}}[R_s(U_d-{E_d}^{\′})+X^{\′}(U_q-{E_q}^{\′})]\\ I_q=\frac{1}{R_s^2+X^{\′2}}[R_s(U_q-{E_q}^{\′})-X^{\′}(U_d-{E_d}^{\′})]\end{array}\right.$

Wherein, R _sfor stator resistance, U _dfor stator terminal voltage d axle component, U _qfor stator terminal voltage q axle component;

The active-power P that induction-motor load absorbs _mand reactive power Q _mbe expressed as:

$\left\{\begin{array}{c}{P}_m=U_d{I}_d+U_q{I}_q\\ Q_m=U_q{I}_d-U_d{I}_q\end{array}\right.$

If have n kind to meet low pressure release conditions with the induction-motor load of low-voltage protection device after fault clearance, the active-power P of induction-motor load _m' and reactive power Q _m' be expressed as:

$\left\{\begin{array}{c}{P_m}^{\′}=(1-k_{\mathrm{mI}}-k_{\mathrm{mII}}-...-k_{\mathrm{mn}})(U_d{I}_d+U_q{I}_q)\\ {Q_m}^{\′}=(1-k_{\mathrm{mI}}-k_{\mathrm{mII}}-...-k_{\mathrm{mn}})(U_q{I}_d-U_d{I}_q)\end{array}\right.$

Wherein, k _mI, k _mII..., k _mnfor with I, II ..., n kind low-voltage protection device the ratio of induction-motor load in total induction-motor load.

In described step 3, active power and the reactive power of integrated load model output are expressed as:

$\left\{\begin{array}{c}P={P_s}^{\′}+{P_m}^{\′}\\ Q={Q_s}^{\′}+{Q_m}^{\′}\end{array}\right.$

Wherein, P and Q are respectively active power and the reactive power of integrated load model output.

Compared with prior art, beneficial effect of the present invention is:

Critical voltage when the present invention introduces load and starts a large amount of excision in the integrated load model of existing consideration distribution network, from lower voltage to critical voltage, start the characteristic parameters such as the time delays of a large amount of excisions, ratio with the load of low-voltage variation in total load to load, be used for describing the characteristic that disturbance shoulder load low-voltage discharges.Integrated load model has overcome traditional load model cannot describe the shortcoming of load low-voltage release characteristics in the time of low-voltage.Make the dynamic characteristic characteristic of approaching to reality load more that in electric system simulation analysis, load shows in the time of low-voltage, for the confidence level that improves electric system simulation analysis provides guarantee.

Brief description of the drawings

Fig. 1 is the integrated load model structure chart of considering load low-voltage release characteristics in the embodiment of the present invention;

Fig. 2 is static load low-voltage release characteristics simulation block diagram in the embodiment of the present invention;

Fig. 3 is induction-motor load low-voltage release characteristics simulation block diagram in the embodiment of the present invention;

Fig. 4 is active power matched curve figure in the embodiment of the present invention;

Fig. 5 is reactive power matched curve figure in the embodiment of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail.

As Fig. 1, the invention provides a kind of integrated load model modeling method of the low-voltage release characteristics of considering to load, described integrated load model comprises static load model and induction-motor load model; Said method comprising the steps of:

Step 1: set up static load model according to static load low-voltage release characteristics;

Step 2: set up induction-motor load model according to induction-motor load low-voltage release characteristics;

Step 3: active power and the reactive power of determining integrated load model output.

As Fig. 2, in described step 1, when before electrical network breaks down and after fault, low-voltage release not yet occurs static load, active power and the reactive power of static load are expressed as:

$\left\{\begin{array}{c}{P}_s=P_{s0}[P_Z{(V/V_0)}^2+P_I(V/V_0)+P_P]\\ Q_s=Q_{s0}[Q_Z{(V/V_0)}^2+Q_I(V/V_0)+Q_P]\end{array}\right.$

Wherein, P _sand Q _sbe respectively electrical network break down before and fault after static load not yet occur low-voltage discharge time static load active power and reactive power; P _s0and Q _s0the active power of static load and reactive power while being respectively stable state; P _zand Q _zbe respectively constant impedance part active power ratio and reactive power ratio in static load; P _iand Q _ibe respectively constant current part active power ratio and reactive power ratio in static load; P _pand Q _pbe respectively firm power part active power ratio and reactive power ratio in static load; V is load bus virtual voltage amplitude, V ₀the busbar voltage of loading during for stable state amplitude;

U _s1be defined as the critical voltage perunit value while starting to excise in a large number with the static load of the 1st kind of low-voltage protection device, t _s1be defined as from lower voltage to U _s1to the time delay that starts a large amount of excisions with the static load of the 1st kind of low-voltage protection device, k _s1for the ratio of the static load with the 1st kind of low-voltage protection device in total static load;

U _s2be defined as the critical voltage perunit value while starting to excise in a large number with the static load of the 2nd kind of low-voltage protection device, t _s2be defined as from lower voltage to U _s2to the time delay that starts a large amount of excisions with the static load of the 2nd kind of low-voltage protection device, k _s2for the ratio of the static load with the 2nd kind of low-voltage protection device in total static load;

U _smbe defined as the critical voltage perunit value while starting to excise in a large number with the static load of m kind low-voltage protection device, t _smbe defined as from lower voltage to U _smto the time delay that starts a large amount of excisions with the static load of m kind low-voltage protection device, k _smfor the ratio of the static load with m kind low-voltage protection device in total static load;

When lower voltage is to U _s1time start timing, reach t in the lasting low-voltage time _s1time, static load low-voltage discharges k _s1static load doubly; When lower voltage is to U _s2time start timing, reach t in the lasting low-voltage time _s2time, static load low-voltage discharges k _s2static load doubly; If fault has m kind to meet low pressure release conditions with the static load of low-voltage protection device after removing, the active-power P of static load _s' and reactive power Q _s' be expressed as:

$\left\{\begin{array}{c}{P_s}^{\′}=P_{s0}(1-k_{s1}-k_{s2}-...-k_{\mathrm{sm}})[P_Z{(V/V_0)}^2+P_I(V/V_0)+P_P]\\ {Q_s}^{\′}=Q_{s0}(1-k_{s1}-k_{s2}-...-k_{\mathrm{sm}})[Q_Z{(V/V_0)}^2+Q_I(V/V_0)+Q_P]\end{array}\right.$

Wherein, k _s1, k _s2..., k _smbe respectively with the 1st, 2 ..., m kind low-voltage protection device the ratio of static load in total static load.

As Fig. 3, in described step 2, when before electrical network breaks down and after fault, low-voltage release not yet occurs induction-motor load, induction-motor load meets:

$\left\{\begin{array}{c}\frac{{{\mathrm{dE}}_d}^{\′}}{\mathrm{dt}}=-\frac{1}{T^{\′}}[{E_d}^{\′}+(X-X^{\′})I_q]-(\mathrm{\ω}-1){E_q}^{\′}\\ \frac{{{\mathrm{dE}}_q}^{\′}}{\mathrm{dt}}=-\frac{1}{T^{\′}}[{E_q}^{\′}-(X-X^{\′})I_d]+(\mathrm{\ω}-1){E_d}^{\′}\\ \frac{\mathrm{d\ω}}{\mathrm{dt}}=-\frac{1}{2H}[({\mathrm{A\ω}}^2+\mathrm{B\ω}+C)T_0-({E_d}^{\′}{I}_d+{E_q}^{\′}{I}_q)]\end{array}\right.$

Wherein, E _d' be motor d axle transient internal voltage, E _q' be motor q axle transient internal voltage; T ' is motor open circuit time constant, T ₀for the benchmark machine torque of motor; A, B and C are machine torque coefficient; X is the reactance of rotor open circuit, and X=X _s+ X _m, wherein X _sfor stator reactance, X _mfor excitatory reactance; Stator equivalent reactance when X ' is rotor stall, and X '=X _s+ X _mx _r/ (X _r+ X _m), X _rfor rotor reactance; ω is the angular speed of rotor; I _dfor stator current d axle component, I _qfor stator current q axle component, be expressed as:

$\left\{\begin{array}{c}{I}_d=\frac{1}{R_s^2+X^{\′2}}[R_s(U_d-{E_d}^{\′})+X^{\′}(U_q-{E_q}^{\′})]\\ I_q=\frac{1}{R_s^2+X^{\′2}}[R_s(U_q-{E_q}^{\′})-X^{\′}(U_d-{E_d}^{\′})]\end{array}\right.$

Wherein, R _sfor stator resistance, U _dfor stator terminal voltage d axle component, U _qfor stator terminal voltage q axle component;

The active-power P that induction-motor load absorbs _mand reactive power Q _mbe expressed as:

$\left\{\begin{array}{c}{P}_m=U_d{I}_d+U_q{I}_q\\ Q_m=U_q{I}_d-U_d{I}_q\end{array}\right.$

U _mIbe defined as the critical voltage perunit value while starting to excise in a large number with the induction-motor load of I kind low-voltage protection device, t _mIbe defined as from lower voltage to U _mIto the time delay that starts a large amount of excisions with the induction-motor load of I kind low-voltage protection device, k _mIfor the ratio of the induction-motor load with I kind low-voltage protection device in total induction-motor load;

U _mIIbe defined as the critical voltage perunit value while starting to excise in a large number with the induction-motor load of II kind low-voltage protection device, t _mIIbe defined as from lower voltage to U _mIIto the time delay that starts a large amount of excisions with the induction-motor load of II kind low-voltage protection device, k _mIIfor the ratio of the induction-motor load with II kind low-voltage protection device in total induction-motor load;

U _mnbe defined as the critical voltage perunit value while starting to excise in a large number with the induction-motor load of n kind low-voltage protection device, t _mnbe defined as from lower voltage to U _mnto the time delay that starts a large amount of excisions with the induction-motor load of n kind low-voltage protection device, k _mnfor the ratio of the induction-motor load with n kind low-voltage protection device in total induction-motor load;

When lower voltage is to U _mItime start timing, reach t in the lasting low-voltage time _mItime, induction-motor load low-voltage discharges k _mIinduction-motor load doubly; When lower voltage is to U _mIItime start timing, reach t in the lasting low-voltage time _mIItime, induction-motor load low-voltage discharges k _mIIinduction-motor load doubly; If have n kind to meet low pressure release conditions with the induction-motor load of low-voltage protection device after fault clearance, the active-power P of induction-motor load _m' and reactive power Q _m' be expressed as:

$\left\{\begin{array}{c}{P_m}^{\′}=(1-k_{\mathrm{mI}}-k_{\mathrm{mII}}-...-k_{\mathrm{mn}})(U_d{I}_d+U_q{I}_q)\\ {Q_m}^{\′}=(1-k_{\mathrm{mI}}-k_{\mathrm{mII}}-...-k_{\mathrm{mn}})(U_q{I}_d-U_d{I}_q)\end{array}\right.$

Wherein, k _mI, k _mII..., k _mnfor with I, II ..., n kind low-voltage protection device the ratio of induction-motor load in total induction-motor load.

In described step 3, active power and the reactive power of integrated load model output are expressed as:

$\left\{\begin{array}{c}P={P_s}^{\′}+{P_m}^{\′}\\ Q={Q_s}^{\′}+{Q_m}^{\′}\end{array}\right.$

Wherein, P and Q are respectively active power and the reactive power of integrated load model output.

Embodiment

For verifying the validity of load model of consideration proposed by the invention load low-voltage release characteristics, get 1 measured data, these data have lost sub-load during voltage disturbance, by the traditional parameters of load model and characteristic parameter substitution load model equation, obtain the matched curve of active power and reactive power as shown in Figure 4 and Figure 5.The matched curve of comparative analysis active power and reactive power, can see while adopting the load model of this consideration load low-voltage release characteristics to carry out matching that effect is significantly better than existing load model, compared with existing load model, the load model of considering load low-voltage release characteristics can be described the low-voltage dropout phenomenon of loading in stability analysis better, make the more system action of approaching to reality of system performance in the calculating of fault post-simulation, improved the confidence level of Simulation Analysis, operation, the control program of working out science for electric power system provide guarantee.

Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit; those of ordinary skill in the field still can modify or be equal to replacement the specific embodiment of the present invention with reference to above-described embodiment; these do not depart from any amendment of spirit and scope of the invention or are equal to replacement, within the claim protection range of the present invention all awaiting the reply in application.

Claims (4)

1. consider the to load integrated load model modeling method of low-voltage release characteristics, is characterized in that: described integrated load model comprises static load model and induction-motor load model; Said method comprising the steps of:

Step 1: set up static load model according to static load low-voltage release characteristics;

Step 2: set up induction-motor load model according to induction-motor load low-voltage release characteristics;

Step 3: active power and the reactive power of determining integrated load model output.

2. the integrated load model modeling method of consideration load low-voltage release characteristics according to claim 1, it is characterized in that: in described step 1, when before electrical network breaks down and after fault, low-voltage release not yet occurs static load, active power and the reactive power of static load are expressed as:

$\left\{\begin{array}{c}{P}_s=P_{s0}[P_Z{(V/V_0)}^2+P_I(V/V_0)+P_P]\\ Q_s=Q_{s0}[Q_Z{(V/V_0)}^2+Q_I(V/V_0)+Q_P]\end{array}\right.$

Wherein, P _sand Q _sbe respectively electrical network break down before and fault after static load not yet occur low-voltage discharge time static load active power and reactive power; P _s0and Q _s0the active power of static load and reactive power while being respectively stable state; P _zand Q _zbe respectively constant impedance part active power ratio and reactive power ratio in static load; P _iand Q _ibe respectively constant current part active power ratio and reactive power ratio in static load; P _pand Q _pbe respectively firm power part active power ratio and reactive power ratio in static load; V is load bus virtual voltage amplitude, V ₀the busbar voltage of loading during for stable state amplitude;

If have m kind to meet low pressure release conditions with the static load of low-voltage protection device after fault clearance, the active-power P of static load _s' and reactive power Q _s' be expressed as:

$\left\{\begin{array}{c}{P_s}^{\′}=P_{s0}(1-k_{s1}-k_{s2}-...-k_{\mathrm{sm}})[P_Z{(V/V_0)}^2+P_I(V/V_0)+P_P]\\ {Q_s}^{\′}=Q_{s0}(1-k_{s1}-k_{s2}-...-k_{\mathrm{sm}})[Q_Z{(V/V_0)}^2+Q_I(V/V_0)+Q_P]\end{array}\right.$

Wherein, k _s1, k _s2..., k _smbe respectively with the 1st, 2 ..., m kind low-voltage protection device the ratio of static load in total static load.

3. the integrated load model modeling method of consideration load low-voltage release characteristics according to claim 1, is characterized in that: in described step 2, when before electrical network breaks down and after fault, low-voltage release not yet occurs induction-motor load, induction-motor load meets:

$\left\{\begin{array}{c}\frac{{{\mathrm{dE}}_d}^{\′}}{\mathrm{dt}}=-\frac{1}{T^{\′}}[{E_d}^{\′}+(X-X^{\′})I_q]-(\mathrm{\ω}-1){E_q}^{\′}\\ \frac{{{\mathrm{dE}}_q}^{\′}}{\mathrm{dt}}=-\frac{1}{T^{\′}}[{E_q}^{\′}-(X-X^{\′})I_d]+(\mathrm{\ω}-1){E_d}^{\′}\\ \frac{\mathrm{d\ω}}{\mathrm{dt}}=-\frac{1}{2H}[({\mathrm{A\ω}}^2+\mathrm{B\ω}+C)T_0-({E_d}^{\′}{I}_d+{E_q}^{\′}{I}_q)]\end{array}\right.$

Wherein, E _d' be motor d axle transient internal voltage, E _q' be motor q axle transient internal voltage; T ' is motor open circuit time constant, T ₀for the benchmark machine torque of motor; A, B and C are machine torque coefficient; X is the reactance of rotor open circuit, and X=X _s+ X _m, wherein X _sfor stator reactance, X _mfor excitatory reactance; Stator equivalent reactance when X ' is rotor stall, and X '=X _s+ X _mx _r/ (X _r+ X _m), X _rfor rotor reactance; ω is the angular speed of rotor; I _dfor stator current d axle component, I _qfor stator current q axle component, be expressed as:

$\left\{\begin{array}{c}{I}_d=\frac{1}{R_s^2+X^{\′2}}[R_s(U_d-{E_d}^{\′})+X^{\′}(U_q-{E_q}^{\′})]\\ I_q=\frac{1}{R_s^2+X^{\′2}}[R_s(U_q-{E_q}^{\′})-X^{\′}(U_d-{E_d}^{\′})]\end{array}\right.$

Wherein, R _sfor stator resistance, U _dfor stator terminal voltage d axle component, U _qfor stator terminal voltage q axle component;

The active-power P that induction-motor load absorbs _mand reactive power Q _mbe expressed as:

$\left\{\begin{array}{c}{P}_m=U_d{I}_d+U_q{I}_q\\ Q_m=U_q{I}_d-U_d{I}_q\end{array}\right.$

If have n kind to meet low pressure release conditions with the induction-motor load of low-voltage protection device after fault clearance, the active-power P of induction-motor load _m' and reactive power Q _m' be expressed as:

$\left\{\begin{array}{c}{P_m}^{\′}=(1-k_{\mathrm{mI}}-k_{\mathrm{mII}}-...-k_{\mathrm{mn}})(U_d{I}_d+U_q{I}_q)\\ {Q_m}^{\′}=(1-k_{\mathrm{mI}}-k_{\mathrm{mII}}-...-k_{\mathrm{mn}})(U_q{I}_d-U_d{I}_q)\end{array}\right.$

Wherein, k _mI, k _mII..., k _mnfor with I, II ..., n kind low-voltage protection device the ratio of induction-motor load in total induction-motor load.

4. the integrated load model modeling method of consideration load low-voltage release characteristics according to claim 1, is characterized in that: in described step 3, active power and the reactive power of integrated load model output are expressed as:

$\left\{\begin{array}{c}P={P_s}^{\′}+{P_m}^{\′}\\ Q={Q_s}^{\′}+{Q_m}^{\′}\end{array}\right.$

Wherein, P and Q are respectively active power and the reactive power of integrated load model output.